JP2005314588A - Continuous manufacturing method of water-absorptive composite sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for continuously and stably manufacturing a water-absorptive composite body uniform in the support level of a water-absorptive polymer. <P>SOLUTION: In the method of continuously manufacturing the water-absorptive composite sheet by polymerizing a polymerizable monomer that gives the water-absorptive polymer in the gas phase in the form of droplets and by dropping the droplets that are under polymerization on a sheet base material that moves at a constant speed, the above polymerizable monomer is sprayed from a spray nozzle into a hollow conical form. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for continuously producing a water-absorbing composite sheet in which a water-absorbing polymer is immobilized on a sheet substrate. In particular, the present invention relates to a method capable of stably and continuously producing a water-absorbing composite sheet having a uniform level of water-absorbing polymer. The water absorbent composite sheet produced by the production method of the present invention is suitably used as a part of a water absorbent article such as a paper diaper or a sanitary napkin.

  The water-absorbing polymer is adhered to the sheet substrate by polymerizing the polymerizable monomer that gives the water-absorbing polymer in the form of droplets in the gas phase, and dropping the droplets during the polymerization onto the sheet substrate. A droplet polymerization method for producing a conductive composite sheet is known. In the droplet polymerization method, a polymerization reaction is generally advanced by jetting and mixing a liquid containing a polymerizable monomer and a liquid containing a polymerization initiator into a gas phase. The droplet polymerization method is particularly effective when the polymerizable monomer is instantaneously polymerized by contact with the polymerization initiator.

  The droplet polymerization method eliminates the pulverization step required for solution polymerization, the separation step between the water-absorbing polymer and the organic solvent, and the organic solvent distillation recovery step required for the reversed-phase suspension polymerization method. It becomes. Depending on the conditions, a part of the heat of polymerization can be used for evaporation of water contained in the water-absorbing polymer, so that the energy load in the subsequent drying process can be reduced, which is very advantageous in terms of energy. There is an advantage of being. Furthermore, according to the droplet polymerization method, it is possible to produce a water-absorbing composite sheet in a short time without handling powder by directly dropping droplets mixed in the gas phase onto the sheet substrate. is there. At this time, a water-absorbing composite sheet having a desired water-absorbing ability can be produced by adjusting the timing of dropping or adjusting the moving speed of the sheet base material. For this reason, by using a droplet polymerization method, a water-absorbing composite sheet having high water-absorbing and water-absorbing speeds and having high water-absorbing polymer particles stably immobilized on a fibrous sheet base material is provided. (See JP-A-9-67403 [Patent Document 1], JP-A 2000-328456 [Patent Document 2]).

In the droplet polymerization method, in order to mix a liquid containing a polymerizable monomer and a liquid containing a polymerization initiator in a gas phase, it is necessary to eject these liquids from nozzles. Various nozzles have been proposed so far as nozzles used in the droplet polymerization method. For example, a spiral injection nozzle including a double concentric spiral injection nozzle as shown in FIG. 1 is known. In the double concentric spiral injection nozzle, a first circular opening (24) for first liquid injection and a second circular opening (25) for second liquid injection are arranged concentrically. The first circular opening (24) is connected to the first guiding portion (21) having a circular cross section, and further, the first liquid follows the spiral trajectory on the inner wall of the first guiding portion. First liquid supply means for supplying the first liquid so as to descend to the first circular opening (24) is provided. A second guide portion (22) having a circular cross section is connected to the second circular opening (25), and further, the second liquid follows the spiral trajectory on the inner wall of the second guide portion. Second liquid supply means for supplying the second liquid so as to descend to the second circular opening (25) is provided. If a first liquid and a second liquid are supplied so as to satisfy a specific condition using a nozzle having such a structure, it is said that a more homogeneous polymer can be produced (Japanese Patent Application Laid-Open No. 2003-40904). No. [Patent Document 3], Japanese Patent Application Laid-Open No. 2003-113203 [Patent Document 4]).
Japanese Patent Laid-Open No. 9-67403 JP 2000-328456 A JP 2003-40904 A JP 2003-113203 A

  However, when the droplet polymerization method is actually performed using these nozzles, the level of water-absorbing polymer supported in the produced water-absorbing composite sheet depends on conditions such as the spraying state of the polymerizable monomer and the arrangement of the nozzles. It became clear that there were problems such as non-uniformity. There is a need in the industry for a water-absorbing composite sheet in which a water-absorbing polymer is more uniformly supported. Therefore, an object of the present invention is to provide a method for continuously and stably producing a water-absorbing composite having a uniform level of water-absorbing polymer and to improve the industrial utility of the droplet polymerization method.

As a result of intensive studies, the present inventors made the spray pattern of the monomer sprayed from the nozzle a hollow conical pattern, and by adjusting the conditions such as the nozzle arrangement as appropriate, the level of water-absorbing polymer supported was uniform. It has been found that a water-absorbent composite sheet can be produced continuously and stably, and the present invention has been provided.
That is, the present invention polymerizes a polymerizable monomer that gives a water-absorbing polymer in the form of droplets in the gas phase, and drops the droplets in progress of polymerization onto a sheet substrate that moves at a constant speed, thereby absorbing water. In the method for continuously producing a water-absorbing composite sheet having a polymer adhered on a sheet substrate, the polymerizable monomer is sprayed in a hollow cone shape from a spray nozzle, and the water-absorbing composite sheet is continuously produced. Provide a method.

In the present invention, it is preferable to use a spiral spray nozzle, particularly a double concentric spiral spray nozzle, as the spray nozzle. In addition, by dropping the droplets containing the polymerizable monomer sprayed in a hollow cone onto a fixed sheet substrate fixed at the same position instead of the moving sheet substrate, the polymerization is completed. When the water-absorbing composite sheet having the water-absorbing polymer adhered on the fixed sheet base material is obtained, the weight-integrated distribution g (r of the water-absorbing polymer with respect to the horizontal distance r (m) from the center of the water-absorbing polymer distribution. ) [W / w] is expressed by the following correlation equation (1) with a correlation coefficient of 0.97 or more, and parameters r _av [m] and σ [m] in the equation are expressed by the following equations (2) and It is preferable to have the relationship of Formula (3).

In the present invention, the polymerizable monomer may be sprayed in a hollow cone shape from a plurality of spray nozzles. At this time, it is preferable that the distance dn [m] between adjacent nozzles satisfies the following relationship.
dn ≧ 0.5 × r _av
Further, when the amount of the water-absorbing polymer supported in the direction perpendicular to the moving direction (hereinafter referred to as the width direction) of the water-absorbent composite sheet produced according to the present invention was statistically analyzed, the average value A _{av of the} supported amount and the standard The deviation Aσ preferably satisfies the following relationship.
Aσ ≦ 0.5 × A _av

  The polymerization in the present invention includes a first liquid composed of a polymerizable monomer solution containing any one of an oxidizing agent and a reducing agent constituting a redox initiator, and the other of the oxidizing agent or the reducing agent contained in the first liquid, Or it is preferable to start by mixing the 2nd liquid consisting of the solution containing the other of the oxidizing agent or reducing agent contained in the 1st liquid, and a polymerizable monomer in a gaseous phase.

  According to the present invention, a water-absorbent composite sheet having a uniform level of water-absorbing polymer can be produced continuously and stably. Since the high-performance water-absorbing composite sheet can be produced in large quantities, the production method of the present invention has high industrial applicability.

BEST MODE FOR CARRYING OUT THE INVENTION

  Below, the manufacturing method of the water absorptive composite sheet of this invention is demonstrated in detail. In the present specification, a numerical range represented by using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.

  The method for producing a water-absorbent composite sheet according to the present invention comprises: a polymerizable monomer that gives a water-absorbing polymer is polymerized in the form of droplets in a gas phase; It is a method for producing a water-absorbing composite sheet in which a water-absorbing polymer adheres onto a sheet base material by being dropped onto the sheet substrate. The characteristic is that the polymerizable monomer is sprayed in a hollow cone shape from the spray nozzle.

  As used herein, the hollow cone is a cone having a tip of the nozzle to which the polymerizable monomer is sprayed or a shape close to a cone, and a shape in which a hollow portion in which no polymerizable monomer is present exists in the cone. Say. The shape of the hollow portion is not particularly limited, and may be conical or spherical. In addition, the hollow conical shape herein may be formed between a certain distance from the nozzle tip, and the hollow conical shape is formed over the entire space where the liquid droplets fall and reach the sheet base material. It is not an essential requirement. When spraying the polymerizable monomer using a plurality of nozzles, it is preferable to spray the polymerizable monomer from each nozzle in a hollow cone shape.

  In order to spray the polymerizable monomer in the shape of a hollow cone, it is preferable to use a spiral injection nozzle. The spiral injection nozzle is a type of nozzle in which a polymerizable monomer is guided in a nozzle while following a spiral trajectory and discharged from an opening of the nozzle. In the present invention, it is preferable to start the polymerization reaction by mixing the two liquids in the gas phase. For this reason, it is particularly preferable to use a double concentric spiral nozzle among the spiral nozzles.

  The double concentric spiral spray nozzle is a nozzle in which two combinations of a guide portion for rotating the supplied liquid and a circular opening for spraying the liquid are formed in a concentric shaft shape. A typical example of such a double concentric spiral injection nozzle will be described with reference to FIG. FIG. 1A is a horizontal sectional view of the upper part of the guiding portion of the double concentric spiral injection nozzle, and FIG. 1B is a vertical sectional view of the double concentric spiral injection nozzle. As shown in FIG. 1 (a), two introduction pipes (23a, 23b) for introducing the first liquid are installed in the first guide part (21). The first liquid is fed in the direction of the arrow through the introduction pipes (23a, 23b), and is vigorously introduced into the first guide part (21). The first liquid reaches the first circular opening (24) while following a spiral trajectory on the inner wall of the first guiding portion (21) by centrifugal force and gravity (FIG. 1 (b)). Similarly, two introduction pipes (23c, 23d) are also installed in the second induction part (22), and the second liquid is urged to the second induction part (22) through the introduction pipes (23c, 23d). It is often introduced and reaches the second circular opening (25) while following a spiral trajectory. The first liquid and the second liquid that have reached the circular opening are ejected with a velocity component in the tangential direction at the opening, as shown in FIG.

  The nozzle shown in FIG. 1 has an inverted conical shape that decreases as the cross-sectional area of the first guide portion (21) goes downward. The cross-sectional area ratio (A1 / B1) between the cross-sectional area A1 of the upper part of the first guiding portion and the cross-sectional area B1 of the first circular opening is not particularly limited as long as the method of the present invention can be performed. A nozzle having a cross-sectional area ratio (A1 / B1) of 9 or less is preferable, a nozzle of 7 or less is more preferable, and a nozzle of 5 or less is more preferable. If a nozzle having a cross-sectional area ratio (A1 / B1) of 9 or less is used, the method of the present invention can be carried out more effectively and simply.

In the present specification, “a cross-sectional area of the upper part of the first guide part” refers to a cross-sectional area of the first guide part at a position where the introduction pipe for supplying the first liquid is connected. The position where the introduction pipe for supplying the first liquid is connected is the upper part of the first guiding part, but is not necessarily the uppermost end of the first guiding part. In other words, the first guide portion may extend further above the position where the introduction pipe is connected. In view of the ease of processing and assembling of each part of the nozzle, the upper portion of the first guide portion is usually cylindrical. In addition, as described above, it is preferable that the first guide portion has a so-called inverted conical shape in which the cross-sectional area becomes smaller toward the lower portion. In the present invention, a nozzle in which an introduction pipe for supplying the first liquid is connected to the boundary between the cylindrical region and the inverted conical region may be used. In this case, the boundary portion is an upper portion of the first guiding portion referred to in the present invention.
When the cross section of the upper part of the first guide part is circular, the cross-sectional area of the upper part of the first guide part is obtained from the inner diameter of the inner wall of the first guide part that the first liquid supplied from the first liquid supply means first contacts. be able to. For example, in the nozzle of FIG. 1B, it is obtained by π (Ds / 2) ² using the inner diameter Ds.
Further, the “cross-sectional area of the first circular opening” in this specification can also be obtained from the inner diameter of the first circular opening when the cross-section is circular. For example, in the nozzle of FIG. 1B, it is obtained by π (Do / 2) ² using the inner diameter Do of the first circular opening.

It is preferable that the length of the first guide portion in the vertical direction is relatively short because attenuation when the liquid descends while following a spiral trajectory can be reduced. The vertical length of the first guiding portion is preferably 0.1 to 5 mm, more preferably 0.1 to 3 mm, and further preferably 0.1 to 1 mm. If the length of the first guide portion in the vertical direction is too short, it tends to be difficult to process the nozzle component.
The first circular opening and the second circular opening may have some variation in the curvature of the opening. Most preferably, the opening is a perfect circle. If the first liquid and the second liquid are ejected from a perfect circular opening, the liquid is not partially biased due to the isotropic ejection.

  The first liquid and the second liquid need to be jetted from the circular opening and merged for the first time in the gas phase. Therefore, it is preferable to devise measures to prevent the two liquid flows from being short-circuited and mixed in the nozzle or the nozzle inlet. For example, as shown in FIG. 2A, it is possible to employ a method of sealing by providing an O-shaped ring (26) or the like in the nozzle assembly portion so that the first liquid and the second liquid are not mixed. However, since the first liquid and the second liquid are introduced into the nozzle at a high pressure, the seal portion of the O-ring is not short-circuited by the liquid pressure during long-term use so that the first liquid and the second liquid are not mixed. It is necessary to pay attention to.

  In order to surely prevent such a short circuit, it is preferable to adopt a structure in which the introduction part of the first liquid and the introduction part of the second liquid are separated and a short circuit due to liquid leakage cannot physically occur. For example, as shown in FIG. 2B, a short circuit can be reliably prevented by completely separating the flow path of the first liquid and the flow path of the second liquid. If such a structure is employed, the relatively difficult assembly work of inserting and sealing the O-shaped ring at a predetermined position with high dimensional accuracy as shown in FIG. Since the liquid nozzle part and the second liquid nozzle part can be fixed and assembled in stages, there is a great practical advantage.

The shape of the double concentric spiral injection nozzle shown in FIGS. 1 and 2 can be changed as appropriate according to the types of the first liquid and the second liquid, the purpose of polymerization, and the like. For example, the number of introduction pipes can be increased or decreased, or the diameter and length of the guiding portion and the inner wall angle can be adjusted.
If a double concentric spiral injection nozzle is used, the first liquid is injected in a hollow conical shape from the inner first liquid opening, and the second liquid is injected in a hollow conical shape from the outer second liquid opening. Can be made. The injection angle and the injection speed are adjusted so that the first liquid and the second liquid collide with each other after the injection. For example, the two liquids may collide by adjusting the injection speed of the first liquid to be higher than the injection speed of the second liquid, or air pressure is applied to either the first liquid or the second liquid. The two liquids may collide efficiently by adjusting the ejection trajectory. In the present invention, the ejection speed and flow rate of the first liquid and the second liquid may be the same or different.

  In the present invention, the polymerizable monomer sprayed in a hollow conical shape from the nozzle falls while being polymerized in the form of droplets in the gas phase. The droplets during polymerization are dropped on a sheet substrate that moves at a constant speed. At this time, the sheet base material may receive all the falling liquid droplets or a part of the liquid droplets. In general, since the number of droplets that fall is small at a point far from the nozzle tip, adjustment is made so that the sheet base material is fed only into a region where a specific range of droplets falls. It is possible. That is, the position at which the sheet base material is fed can be adjusted so that the amount of the water-absorbing polymer supported is substantially uniform over the entire water-absorbing composite sheet to be manufactured.

  The sheet substrate is moved at a constant speed to receive the falling droplets. By moving at a constant speed, continuous and stable production can be realized, and the same product can be mass-produced industrially. In the present invention, the sheet base material may be a belt-like continuous body or a plurality of independent bodies. In the case of a belt-like continuous body, a sheet base material wound up on a roll or the like is drawn out at a constant speed to receive a falling liquid droplet, and then subjected to a heat treatment or the like, and then wound up again on another roll, It can be cut into a size and stored. In addition, when the sheet base material is a plurality of independent bodies, the droplets are received while being moved side by side on a conveyor or the like driven at a constant speed, and then subjected to heat treatment and stored. Is possible. In the latter case, it is possible to preferably employ an embodiment in which a plurality of sheet base materials are arranged on a net-like conveyor belt and air is drawn downward to enhance the adhesion between the sheet base material and the conveyor belt. .

The material of the sheet base material used in the present invention is such that the falling droplets during the polymerization are easily attached and the water-absorbing polymer formed by the polymerization is difficult to drop off from the sheet base material. The type and structure are not particularly limited. In general, a sheet-like fibrous base material is used, and specifically, cloth, paper, pulp, non-woven fabric and the like can be used. Among them, it is preferable to use fluff pulp or nonwoven fabric in which the fibrous base material is roughly accumulated, the polymer particles can easily enter the inside, and the polymer particles can strongly adhere to the fibrous base material. Particularly preferred is a non-woven fabric made of (semi) synthetic fibers such as polyester, polyolefin, polyamide, acetate, etc., which has high strength even in a wet state. The fiber thickness of the fibrous base material constituting the nonwoven fabric is preferably 10 to 50 μm, and the basis weight of the nonwoven fabric is preferably 10 to 100 g / m ² , particularly preferably 20 to 50 g / m ² .

  In accordance with the present invention, by receiving droplets falling on a sheet substrate that moves at a constant speed, the loading profile of the water-absorbing polymer in the direction perpendicular to the moving direction (width direction) is fixed. A water-absorbing composite sheet can be produced with a high yield. In particular, when the polymerizable monomer is sprayed in the shape of a hollow cone according to the present invention, there is an advantage that the carrying amount profile in the width direction can be brought into a uniform state with relatively little unevenness.

In the present invention, a droplet containing a polymerizable monomer sprayed in a hollow conical shape is dropped on a fixed sheet substrate fixed in the same position instead of a moving sheet substrate to complete the polymerization. When the water-absorbing composite sheet having the water-absorbing polymer attached on the fixed sheet substrate is obtained, the weight-integrated distribution g of the water-absorbing polymer with respect to the horizontal distance r (m) from the center of the water-absorbing polymer distribution g ( r) [w / w] is expressed by the above correlation equation (1) with a correlation coefficient of 0.97 or more, and parameters r _av [m] and σ [m] in the equation are expressed by the above equation (2) And it is preferable to adjust so as to have the relationship of Formula (3). A correlation coefficient of 0.97 or more means that the level of water-absorbing polymer supported is fairly uniform.

Here, r _av represents the distance r corresponding to the weight integrated fraction of 50%, and the larger the _rav , the wider the monomer spray angle. On the other hand, σ represents the spread of the distribution. If σ is small, the distribution becomes sharp, and the maximum distribution region of the water-absorbing polymer becomes a hollow circle (doughnut shape), and the distribution amount decreases toward the center and the circumference of the circle. Conversely, if σ is large, a broad distribution is obtained, and the distribution amount of the water-absorbing polymer gradually decreases toward the periphery of a certain point as a maximum.
To obtain a high-performance water-absorbent composite sheet which uniformly carries the water-absorbing polymer, r _av is preferably at 0.2m or more. r _av is more preferably 0.25 m or more, and further preferably 0.3 m or more. If r _av is too small, it is intensively dispersed at the center of the spray region, and the amount of polymer supported during continuous production tends to be non-uniform. If r _av is 0.2 m or more, excessive concentration can be avoided, and if r _av is 0.3 m or more, the level becomes quite satisfactory and the water-absorbing polymer support level tends to be uniform.

On the other hand, σ is preferably 0.5 × r _av or less, more preferably 0.4 × r _av or less, and further preferably 0.3 × r _av or less. If σ is too large compared to r _av , a broad distribution, that is, a wide distribution spreads in a solid circular shape toward the periphery centering on the portion showing the maximum supported amount, and the resulting water-absorbing composite The water-absorbing polymer carrying level of the body sheet becomes non-uniform. If it is 0.5 × r _av or less, the distribution is narrow, and if it is 0.3 × r _av or less, the level becomes quite satisfactory and the water-absorbing polymer support level tends to be uniform.

The water-absorbing composite sheet produced by the method of the present invention has a uniform level of water-absorbing polymer supported as compared with the water-absorbing composite sheet produced by the conventional method. When the water-absorbing composite sheet produced by the method of the present invention was statistically analyzed for the amount of the water-absorbing polymer supported in the width direction, the average value A _av and the standard deviation Aσ of the amount supported were Aσ ≦ 0.5 × A It is preferable to satisfy the relationship of _av . Aσ is more preferably 0.4 × A _av or less, and further preferably 0.3 × A _av or less. Here, the smaller the Aσ / A _av , the more uniform the water-absorbing polymer support level in the width direction. If Aσ ≦ 0.5 × A _av , the water-absorbing polymer carrying level is uniform compared to the water-absorbent composite sheet produced by the conventional method, and if Aσ ≦ 0.3 × A _av , the water absorption The polymer loading level is uniform enough to be fully satisfactory. Table 2 and FIGS. 3 to 5 can be referred to for specific examples.

  Industrially, it is necessary to produce a large amount of a water-absorbent composite sheet at high speed. For this reason, in the method of this invention, a scale-up can be aimed at using a some nozzle. That is, by arranging a plurality of nozzles at appropriate intervals and spraying the polymerizable monomer from each nozzle, a water absorbent composite sheet in which the water absorbent polymer is uniformly supported over a wider range can be obtained. The arrangement positions of the plurality of nozzles are appropriately adjusted according to the width of the sheet base material, the moving speed of the sheet base material, the shape of the nozzle, the spraying speed from the nozzle, and the like. For example, a mode in which a plurality of nozzles are arranged at equal intervals in the same direction as the moving direction of the sheet base material can be mentioned. At this time, it is preferable to arrange a plurality of nozzles at equal intervals directly above the center line of the sheet base material (the same direction as the movement direction). By adopting such an embodiment, it becomes possible to quickly and easily produce a water absorbent composite sheet having a large amount of water absorbent polymer supported. Moreover, the aspect which arranges a some nozzle at equal intervals on the straight line (width direction) orthogonal to the moving direction of a sheet | seat base material as another aspect can also be mentioned. By adopting such an embodiment, it is possible to carry a water-absorbing polymer widely and uniformly in the width direction of the sheet base material, so that a larger water-absorbing composite sheet can be produced with high performance. You may combine these aspects suitably.

The distance from the surface on which the sheet base material is moved to each nozzle is preferably the same, but the distance may be changed depending on the nozzle. The distance dn between adjacent nozzles is preferably 0.5 × r _av or more, more preferably 0.6 × r _av or more, and further preferably 0.7 × r _av or more. . If the distance between the nozzles is too short compared to the monomer spray range, the stability of the nozzles is impaired. On the other hand, if the length is too long, the polymerization tank becomes large and uneconomical.

Conditions satisfying these parameters can be set by calculation and trial and error in a preliminary experiment using the fixed sheet of the above ([0026] to [0031]).
In the present invention, a polymerizable monomer that provides a water-absorbing polymer is supplied to each nozzle. Preferably, the first liquid and the second liquid that can start the polymerization reaction by mixing with each other are supplied to separate paths in the nozzle and mixed with each other immediately after injection. If the double concentric spiral injection nozzle shown in FIGS. 1 and 2 is used, such an embodiment can be implemented.

  When carrying out the present invention using the first liquid and the second liquid, the polymerizable monomer and the polymerization initiator are generally contained in at least one of the first liquid and the second liquid, respectively. . Specifically, a first liquid composed of a polymerizable monomer solution containing any one of an oxidizing agent and a reducing agent constituting the redox initiator, and the other of the oxidizing agent or the reducing agent contained in the first liquid, or The 2nd liquid which consists of a solution containing the other of the oxidizing agent or reducing agent contained in the 1st liquid and a polymerizable monomer can be illustrated.

  The kind of the polymerizable monomer used in the present invention is not particularly limited. For example, a vinyl compound, a vinylidene compound, a vinylene compound, a cyclic olefin compound and the like can be appropriately selected and used depending on the application. These polymerization monomers are roughly classified into water-soluble polymerization monomers and oil-soluble polymerization monomers depending on the type of substituent. Examples of the water-soluble polymerization monomer include olefinic unsaturated carboxylic acid or a salt thereof, olefinic unsaturated sulfonic acid or a salt thereof, olefinic unsaturated amine, and olefinic unsaturated amide. Examples of the oil-soluble polymerization monomer include styrene, isobutene, vinyl chloride, vinyl acetate, acrylic acid esters, and methacrylic acid esters. For specific examples and reaction examples of the polymerizable monomer that can be used in the present invention, reference can be made to Takayuki Otsu, “Chemistry of Polymer Synthesis” (Chemical Doujin), pages 34 to 43, and the like. These monomers may be used alone or in combination of two or more.

  By applying the present invention to various monomers, various polymers conventionally obtained by solution polymerization, emulsion polymerization, and suspension polymerization can be efficiently produced. In addition, soap-free polymerization can be achieved by applying a polymerizable monomer that has been conventionally used for emulsion polymerization or suspension polymerization to the present invention. In the present invention, the polymer structure is controlled (for example, the construction of the core-shell structure, the production of the microcapsule, the production of the block polymer) by selecting the monomer species and controlling the mixing state of the two liquids. Is also possible.

  When producing a water-absorbing polymer, an aliphatic unsaturated carboxylic acid or a salt thereof is preferably selected as the polymerizable monomer. Specifically, acrylic acid or a salt thereof as a vinyl compound, unsaturated monocarboxylic acid or a salt thereof such as methacrylic acid or a salt thereof as a vinylidene compound, maleic acid or a salt thereof, fumaric acid or a salt thereof, itaconic acid Or unsaturated dicarboxylic acid, such as its salt, or its salt can be illustrated. These may be used alone or in admixture of two or more. Among these, acrylic acid or a salt thereof and methacrylic acid or a salt thereof are preferable, and acrylic acid or a salt thereof is particularly preferable. When producing a water-soluble or water-absorbing polymer, these aliphatic unsaturated carboxylic acids or salts thereof are preferably used in an amount of 50 mol% or more, more preferably 80 mol% or more based on the total amount of the polymerizable monomer. More preferred.

  As the salt of the aliphatic unsaturated carboxylic acid, a water-soluble salt such as an alkali metal salt, an alkaline earth metal salt, or an ammonium salt is usually used. The degree of neutralization is appropriately determined according to the purpose. In the case of acrylic acid, it is preferable that 20 to 90 mol% of the carboxyl group is neutralized with an alkali metal salt or an ammonium salt. When the degree of partial neutralization of the acrylic acid monomer is less than 20 mol%, the water absorption ability of the resulting water-absorbing polymer tends to be remarkably lowered.

  For neutralization of the acrylic acid monomer, an alkali metal hydroxide, bicarbonate or the like or ammonium hydroxide can be used, but an alkali metal hydroxide is preferable, and a specific example thereof is water. Sodium oxide and potassium hydroxide are mentioned.

  In the present invention, in addition to the aliphatic unsaturated carboxylic acid, polymerizable monomers copolymerizable therewith, for example, (meth) acrylamide, (poly) ethylene glycol (meth) acrylate, 2-hydroxyethyl (meth) acrylate Can be copolymerized. Moreover, although it is a low water-soluble monomer, it can be copolymerized in such an amount that does not deteriorate the performance of the water-absorbing polymer that produces alkyl acrylates such as methyl acrylate and ethyl acrylate. In this specification, the term “(meth) acryl” means both “acryl” and “methacryl”.

  The concentration of the polymerizable monomer contained in the polymerizable monomer-containing liquid used in the present invention can be appropriately determined according to the purpose. For example, in the case of a polymerizable monomer-containing liquid containing an aliphatic unsaturated carboxylic acid or a salt thereof as a main component, the concentration of the polymerizable monomer is preferably 20% by weight or more, more preferably 25% by weight or more. preferable. When the concentration is less than 20% by weight, the polymerization rate tends to be too slow, and as a result, the water absorption ability of the water-absorbing polymer after polymerization tends to be insufficient. The upper limit is preferably about 80% by weight from the handling of the polymerization reaction solution.

  The polymerizable monomer-containing liquid used in the present invention may contain a crosslinking agent. For example, an aliphatic unsaturated carboxylic acid or a salt thereof, particularly acrylic acid or a salt thereof may form a self-crosslinking polymer by itself, but if a cross-linking agent is used in combination, a crosslinked structure can be positively formed. it can. Moreover, when a crosslinking agent is used in combination, the water absorption performance of the generally formed water absorbing polymer is improved. The crosslinking agent may be a divinyl compound copolymerizable with the polymerizable monomer, for example, N, N′-methylenebis (meth) acrylamide, (poly) ethylene glycol (meth) acrylates, etc., and 2 which can react with carboxylic acid. Water-soluble compounds having one or more functional groups, for example, polyglycidyl ethers such as ethylene glycol diglycidyl ether and polyethylene glycol diglycidyl ether are preferably used. Of these, N, N'-methylenebis (meth) acrylamide is particularly preferred. The amount of the crosslinking agent used is 0.001 to 1% by weight, preferably 0.01 to 0.5% by weight, based on the charged amount of monomer. In addition, you may contain these crosslinking agents in an initiator liquid mixture.

  In addition to the above, materials described in JP-A-9-255704 [0012] to [0015] can also be used in the method of the present invention.

The kind of the polymerization initiator used in the method of the present invention is not particularly limited as long as it can initiate polymerization of the polymerizable monomer.
For example, a thermal decomposition type polymerization initiator such as a peroxide such as benzoyl peroxide, acetyl peroxide, lauroyl peroxide, or an azo compound such as azobisisobutyronitrile can be used. Moreover, the above redox polymerization initiators can be preferably used. In general, it is preferable to use a redox polymerization initiator comprising a combination of a radical generator (oxidant) exhibiting oxidizing properties and a reducing agent.

Examples of the oxidizing agent for the aqueous redox polymerization initiator include persulfate and hydrogen peroxide. Examples of the reducing agent for the aqueous redox polymerization initiator include inorganic reducing agents such as ferrous salt and sodium sulfite, and organic reducing agents such as alcohols, amines, and ascorbic acid.
Examples of the oxidizing agent for the non-aqueous redox polymerization initiator include hydroperoxides such as t-butyl hydroperoxide and cumene hydroperoxide, dialkyl peroxides, and diacyl peroxides. Examples of the reducing agent for the non-aqueous redox polymerization initiator include tertiary amines, naphthenic acid salts, mercaptans, and the like.
The oxidizing agent of the redox polymerization initiator is preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer. The reducing agent of the redox polymerization initiator is preferably used in an amount of 0.01 to 10% by weight, particularly 0.1 to 2% by weight, based on the polymerizable monomer.

  In addition to the above, materials and techniques described in Takayuki Otsu's “Revised Polymer Synthesis Chemistry” (Chemical Doujin), pages 59-69 can also be used for the polymerization initiator.

  The polymerization rate at the time when the droplets in progress of polymerization are in contact with the gas phase or on the sheet substrate to form an aggregated granular material is 3 to 97%, preferably 20 to 97%, more preferably 50 to 95%. Set the conditions so that If this polymerization rate is too low, even if the droplets collide with each other, they do not become agglomerated particles but are integrated into large particles, or when the droplets fall on the sheet substrate, It spreads or is absorbed or impregnated, making it difficult to adhere to the sheet substrate in the form of agglomerated granules. Moreover, when too high, the adhesive force with a base material will not be expressed, but the fixing property of a sheet base material and a water absorbing polymer will worsen.

The water-absorbing polymer is preferably attached to the sheet substrate so that the amount of the water-absorbing composite sheet finally obtained is 50 to 400 g / m ² . Although it depends on the application, it is generally more preferable to deposit so as to be 80 to 300 g / m ² . When the amount of the water-absorbing polymer supported on the water-absorbing composite sheet is small, the water-absorbing ability is naturally reduced. Moreover, when there is too much content, it is generally uneconomical, and the ratio of the part couple | bonded with a sheet base material reduces, and the bond strength with a sheet base material becomes weak.

  The particles of the water-absorbing polymer constituting the water-absorbing composite sheet produced by the method of the present invention are composed of at least a part of polymer particles (primary particles) being polymerized to form an aggregated granular material. In addition, it is preferable that a part of the polymer particles (primary particles) constituting the aggregated granular material are not directly bonded to the sheet base material. Since such agglomerated granular material has a large specific surface area, the water absorption speed is large, and only a part of the primary particles constituting the agglomerated granular material is bonded to the sheet base material. Restraint received from is small and has excellent water absorption ability. In addition, since the joint surfaces of the primary particles constituting the aggregated granular material are integrated, the aggregated granular material is less likely to collapse into primary particles and fall off from the sheet base material before and after water absorption. . It is preferable that 30% by weight or more of the polymer particles are agglomerated granules, and more preferably 50% by weight or more, particularly 80% by weight or more are agglomerated granules. In general, the larger the ratio of the aggregated granular material, the better the performance as a water absorbing material. The particle diameter of the aggregated granular material is preferably substantially in the range of 100 to 3000 μm. When the particle size is smaller than 100 μm, the water absorption performance tends to be insufficient. On the other hand, when the particle size is larger than 3000 μm, the adhesive force to the sheet substrate tends to be weakened. The ratio and particle size of the aggregated granular material can be controlled mainly by appropriately adjusting the density, distribution state, flow state and the like of the particles in the gas phase during polymerization. For example, in order to increase the ratio of the agglomerated particles, the amount of polymer dropped per unit cross-sectional area of the polymerization chamber can be increased or the polymerization chamber can be increased so that the chance of particles in the polymerization process coming into contact with each other during the fall increases. It is sufficient to generate an upward flow to slow down the falling speed of the polymer particles. Another method is to generate a drift in the polymerization chamber and cause the distribution of the falling polymer particles to be shifted.

  After applying the water-absorbing polymer to the sheet substrate, the water-absorbing composite is obtained by appropriately performing the water content adjustment step, the drying step, the fiber opening step, the sieving step, the molding step, the surface cross-linking step, the residual monomer treatment step, etc. Can be obtained.

  The water-absorbent composite sheet produced by the method of the present invention can be used in various applications where water-absorbing polymers have been used so far. "Water-absorbing polymer", pages 81-111 (Fusayoshi Masuda, Kyoritsu Shuppan, 1987), "Development trend of superabsorbent resin and its application development" (Eizo Omori, Techno Forum, 1987), Kenji Tanaka, "Industrial Materials" 42, No. 4, pp. 18-25, 1994, Nobuyuki Harada, Tadao Shimomura, pp. 26-30, various uses of the water-absorbing polymer are introduced, and for such uses, they are produced by the method of the present invention. A water-absorbing composite sheet can also be used as appropriate. For example, paper diapers, sanitary products, freshness-keeping materials, moisturizing agents, cold-retaining agents, anti-condensation agents, soil improvement materials and the like can be mentioned.

  Furthermore, JP-A 63-267370, JP-A 63-10667, JP-A 63-295251, JP-A 63-270801, JP-A 63-294716, JP 64-64602, JP-A-1-231940, JP-A-1-243927, JP-A-2-30522, JP-A-2-153373, JP-A-3-21385, JP-A-4-213 It can also be used for applications of the water-absorbent composite sheet proposed in Japanese Patent No. 133728, Japanese Patent Laid-Open No. 11-156188, and the like.

  The features of the present invention will be described more specifically with reference examples, examples, comparative examples and test examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.

(Reference Example 1)
To 100 parts by weight of acrylic acid, 133.3 parts by weight of a 25% by weight aqueous sodium hydroxide solution and 3.3 parts by weight of distilled water were added, and a partially neutralized aqueous acrylic acid solution having a monomer concentration of 50% by weight and a neutralization degree of 60 mol% was obtained. Prepared. To 100 parts by weight of the partially neutralized acrylic acid aqueous solution, 0.14 parts by weight of N, N′-methylenebisacrylamide as a crosslinking agent and 4.55 parts by weight of a 31% by weight hydrogen peroxide aqueous solution as an oxidizing agent were added. Solution A was prepared. In addition to this, 0.14 parts by weight of N, N′-methylenebisacrylamide as a crosslinking agent and 0.57 parts by weight of L-ascorbic acid as a reducing agent with respect to 100 parts by weight of the partially neutralized acrylic acid aqueous solution. Was added to prepare Solution B. The prepared solution A and solution B were each maintained at a temperature of 20 ° C. in a jacketed stainless steel kettle having a temperature control function.

Solution A and Solution B were respectively supplied from a kettle through a heat exchanger to a spiral injection nozzle installed in the upper part of a polymerization tank having an inner diameter of 1.5 m and a height of 3.5 m by a fixed supply pump. The heat exchanger used here has a structure in which about 4 m (heat transfer area: about 0.08 m ² ) is passed through a pipe (inner diameter: 4 mm, outer diameter: 6 mm) for flowing the solution through a hot water tank whose temperature is controlled. With this heat exchanger, the solution A and the solution B sprayed from the nozzle were controlled to be (25 ± 0.5) ° C., respectively. Moreover, the spiral injection nozzle used the double concentric spiral injection nozzle which has the structure shown in FIG. 1, and supplied the solution A to the inner side and the solution B to the outer side. The size of the double concentric spiral spray nozzle and the flow rates of solution A and solution B were as follows.
Solution A (nozzle inside) Diameter of circular opening 1mm
Entrance area 1.6mm ²
Diameter of the upper part of the guide part 2mm
Flow rate 400ml / min
Solution B (nozzle outside) Area of circular opening 3mm
Entrance area 9.6mm ²
12mm diameter at the top of the guide
Flow rate 400ml / min

Solution A and Solution B were jetted from the circular opening of the nozzle and then collided and atomized in the vicinity of the circular opening, and dropped into the gas phase (in air, at a temperature of 50 ° C.) as polymerization progressed as droplets. .
When the polymerization was stabilized, a polyester nonwoven fabric substrate (weight per unit: 30 g / m ² , 1 m square) was inserted for 1 minute 3 m below the tip of the circular opening of the nozzle to complete the polymerization on the substrate. .
Through this compounding step, the water-absorbing polymer was supported on the substrate. Thereafter, the polymer supported by a 110 ° C. hot air dryer was dried to obtain a water-absorbing composite sheet in which the water-absorbing polymer was supported on a 1 m square base material.

(Reference Example 2)
In Reference Example 1, a water-absorbing composite sheet was obtained in accordance with the same method except that the flow rate of the solution A was 300 ml / min.

(Test Example 1)
The water-absorbing composite sheets obtained in Reference Example 1 and Reference Example 2 were evaluated by the following procedure, and the weight integrated distribution formula of the water-absorbing polymer was estimated.
A circle is cut out from the center of the distribution of the water-absorbing polymer carried on the fiber substrate until the water-absorbing polymer is no longer carried in steps of 5 cm in radius, one water-absorbing composite having a radius of 5 cm carrying the water-absorbing polymer, 5-10 cm, 10-15 cm, ... donut-shaped water-absorbing composites were obtained. Each weight was measured, and the weight integrated distribution of the water-absorbing polymer at each radial position was determined. The accumulated weight distribution of the obtained water-absorbing polymer is considered to be the same as the accumulated weight distribution of the monomers during polymerization during polymerization.
The weight fraction of each water-absorbing composite obtained here was divided by the area to obtain the probability density.
The unknown parameters r _av and σ were estimated by the Marcat method so that the obtained probability density matched the following probability density function f (r).

  As a result of the evaluation, the weight integrated distribution of the water-absorbing polymer in Reference Example 1 and Reference Example 2 was as shown in the following table.

(Example 1)
In the method of Reference Example 1, when the polymerization was stabilized, a strip-shaped polyester nonwoven fabric substrate (weight per unit area: 30 g / m ² ) having a width of 1 m was formed at a speed of 3 m / min, 3 m below the tip of the circular opening of the nozzle. It was conveyed in the horizontal direction, and the water-absorbing polymer was supported on the nonwoven fabric. This operation was stably continued for about 30 minutes.
The obtained continuous water-absorbing composite sheet was cut 10 cm in the longitudinal direction at a position 15 minutes after the start of operation, dried the water-absorbing polymer supported by a 110 ° C. hot air dryer, and further cut in 10 cm increments in the sheet width direction. Thus, a 10 cm square water-absorbing composite was obtained.

(Comparative Example 1)
In the method of Reference Example 2, when the polymerization was stabilized, a strip-shaped polyester nonwoven fabric substrate (weight per unit area: 30 g / m ² ) having a width of 1 m was formed at a speed of 2 m / min 3 m below the tip of the circular opening of the nozzle. It was conveyed in the horizontal direction, and the water-absorbing polymer was supported on the nonwoven fabric. This operation was stably continued for about 30 minutes.
The obtained continuous water-absorbing composite sheet was cut 10 cm in the longitudinal direction at a position 15 minutes after the start of operation, dried the water-absorbing polymer supported by a 110 ° C. hot air dryer, and further cut in 10 cm increments in the sheet width direction. Thus, a 10 cm square water-absorbing composite was obtained.

(Example 2)
Two nozzles used in Reference Example 1 were prepared and installed such that the distance between the nozzle tips (distance between nozzles) was 20 cm. Polymerization was carried out under the same conditions as in Reference Example 1. When the polymerization is stable, a belt-like polyester nonwoven fabric substrate (width 1 m, basis weight 30 g / m ² ) is conveyed at a speed of 6 m / min 3 m below the tip of the circular opening of the nozzle, and the water-absorbing polymer is placed on the nonwoven fabric. It was made to carry on. At this time, the tips of the two nozzles were positioned at the same height immediately above the center line of the polyester nonwoven fabric base material (virtual line in the longitudinal direction passing through the inside by 50 cm from both ends). This operation was stably continued for about 30 minutes.
The obtained continuous water-absorbing composite sheet was cut 10 cm in the longitudinal direction at a position 15 minutes after the start of operation, dried the water-absorbing polymer supported by a 110 ° C. hot air dryer, and further cut in 10 cm increments in the sheet width direction. Thus, a 10 cm square water-absorbing composite was obtained.

(Comparative Example 2)
In Example 2, the polymerization was performed in the same manner except that the distance between the nozzles was 10 cm. Approximately 5 minutes after the start of operation, polymer adhered to the tip of one nozzle, making it impossible to continue the operation.

(Test Example 2)
With respect to ten 10 cm square water-absorbing composite sheets obtained in Examples 1 and 2 and Comparative Example 1, the amount of the water-absorbing polymer supported was measured according to the following procedure.
(1) The weight of the water-absorbent composite sheet was measured and designated as Wc (unit: g).
(2) The water-absorbing composite sheet was placed in a 50 ml sealed glass container, and an aqueous solution in which 0.03 g of L-ascorbic acid was dissolved in 25 g of distilled water was added to swell and held at 40 ° C. for 24 hours.
(3) After that, the contents of the glass container were suction filtered with an aspirator having a final vacuum of 10 to 25 mmHg with a filter paper that had been dried under reduced pressure at 80 ° C. for 3 hours to a constant weight value, and the fibers on the filter paper were thoroughly washed , Dried at 100 ° C. for 5 hours and precisely weighed, and the value was defined as Wf (unit: g).
(4) Wc-Wf was calculated and used as the amount of water-absorbing polymer supported.

Data of the measured amount of the water-absorbing polymer supported was graphed with the horizontal axis representing the distance from the center line and the vertical axis representing the supported amount. The center line here means a virtual line passing through the center of the water-absorbent composite sheet (sheet base material). The center line is parallel to the moving direction of the sheet base material in the manufacturing process. The water-absorbing composite sheet of Example 1 is shown in FIG. 3, the water-absorbing composite sheet of Comparative Example 1 is shown in FIG. 4, and the water-absorbing composite sheet of Example 2 is shown in FIG. Further, the carrying amount of the water-absorbing polymer was statistically analyzed, and the average value A _av and the standard deviation Aσ of the carrying amount were obtained and as shown in the following table.

  As is apparent from FIGS. 3 to 5, the amount of the water-absorbing polymer supported by the water-absorbing composite sheet (Comparative Example 1) produced by the method other than the present invention decreases toward the both ends with the center line as the maximum. It was. In contrast, the water-absorbing composite sheets (Example 1 and Example 2) produced by the method of the present invention have a wide range in which the amount of the water-absorbing polymer supported is almost constant, and realize a more uniform distribution. It had been. In addition, since almost the same results were obtained in Example 1 and Example 2, the water-absorbing polymer was made uniform quickly and stably by increasing the number of nozzles and increasing the moving speed of the sheet base material in the method of the present invention. It was also revealed that a water-absorbing composite sheet supported on the substrate can be produced.

(Test Example 3)
About ten 10 cm square water-absorbing composite sheets obtained in Examples 1 and 2 and Comparative Example 1, the water retention capacity was measured according to the following procedure.
(1) A necessary amount of physiological saline (0.9 wt% sodium chloride aqueous solution) was prepared in advance.
(2) The water absorbent composite sheet was further cut so that the amount of the water absorbent polymer supported on the water absorbent composite sheet was about 1 g. The weight of the water-absorbing polymer at that time was W1 (unit: g). However, when the weight of the water-absorbing polymer was less than 1 g in 10 cm square, all 10 cm water-absorbing composite sheets were used.
(3) The sample of (2) was put in a 250 mesh nylon bag (20 cm × 10 cm) and immersed in 500 ml of physiological saline at room temperature for 30 minutes.
(4) The nylon bag was then pulled up, suspended for 15 minutes and drained, and then dehydrated at 90 G for 90 seconds using a centrifuge.
(5) The weight W2 (unit: g) of the nylon bag containing the dehydrated sample was measured.
(6) The same fiber as that constituting the sheet base material of the water-absorbent composite sheet is cut out so as to have the same weight as that contained in the above sample, and a 250-mesh nylon bag (20 cm × 10 cm) as before. ) And immersed in 500 ml of physiological saline at room temperature for 30 minutes.
(7) The nylon bag was then pulled up, suspended for 15 minutes and drained, and then dehydrated at 90 G for 90 seconds using a centrifuge. The weight W3 (unit: g) of the nylon bag containing the dehydrated fiber was measured.
(8) The water retention capacity S of physiological saline was calculated according to the following formula.
W2-W3
Water retention capacity S = ―――――――――
W1

The measured water retention capacity was graphed with the horizontal axis representing the distance from the center line and the vertical axis representing the water retention capacity. The results of graphing the water retention capacity in the width direction for the water-absorbent composite sheets of Example 1, Comparative Example 1, and Example 2 are shown in FIG. 6, FIG. 7, and FIG.
As is clear from FIGS. 6 to 8, the water-absorbing composite sheet (Comparative Example 1) produced by the method other than the present invention had a considerable variation in water retention capacity depending on the position in the width direction. On the other hand, the water-absorbing composite sheets (Example 1 and Example 2) produced by the method of the present invention had a substantially constant water retention ability regardless of the position in the width direction. This indicates that in the water-absorbent composite sheet produced by the method of the present invention, the supported water-absorbing polymer uniformly exhibits high water retention ability, and the water-absorbing polymer is efficiently distributed. . In addition, since almost the same results were obtained in Example 1 and Example 2, by increasing the number of nozzles and increasing the moving speed of the sheet base material in the method of the present invention, high-performance water absorption can be achieved quickly and stably. It has also been found that composite sheets can be produced.

  According to the present invention, a water-absorbent composite sheet having a uniform level of water-absorbing polymer can be produced continuously and stably. Since the high-performance water-absorbing composite sheet can be produced in large quantities, the production method of the present invention has high industrial applicability.

It is sectional drawing and a perspective view which show the specific example of a double concentric spiral injection nozzle. It is sectional drawing which shows the specific example of a double concentric spiral injection nozzle. It is a graph which shows the result of having measured the change of the load of the water absorption polymer of the width direction about the water absorptive composite sheet of Example 1 (refer to test example 2). It is a graph which shows the result of having measured the change of the load of the water absorption polymer of the width direction about the water absorption composite sheet of comparative example 1 (refer to test example 2). It is a graph which shows the result of having measured the change of the load of the water absorption polymer of the width direction about the water absorptive composite sheet of Example 2 (refer to test example 2). It is a graph which shows the result of having measured the change of the water retention ability of the width direction about the water absorptive composite sheet of Example 1 (refer to test example 3). It is a graph which shows the result of having measured the change of the water retention ability of the width direction about the water absorptive composite sheet of comparative example 1 (refer to test example 3). It is a graph which shows the result of having measured the change of the water retention ability of the width direction about the water absorptive composite sheet of Example 2 (refer to test example 3).

Explanation of symbols

21 First guide
22 2nd induction | guidance | derivation part 23a, 23b 1st introduction pipe 23c, 23d 2nd introduction pipe
24 1st circular opening
25 Second circular opening
26 O-type ring

Claims (8)

  The polymerizable monomer that gives the water-absorbing polymer is polymerized in the form of droplets in the gas phase, and the droplets in progress of polymerization are dropped onto a sheet substrate that moves at a constant speed, so that the water-absorbing polymer becomes a sheet base. In the method for continuously producing a water-absorbing composite sheet adhered on a material, the polymerizable monomer is sprayed in a hollow conical shape from a spray nozzle, and the water-absorbing composite sheet is continuously produced.   The said spray nozzle is a spiral injection nozzle, The continuous manufacturing method of the water absorptive composite sheet | seat of Claim 1 characterized by the above-mentioned.   The said spray nozzle is a double concentric spiral spray nozzle, The continuous manufacturing method of the water absorptive composite sheet | seat of Claim 1 characterized by the above-mentioned. Water droplets containing the polymerizable monomer sprayed in the form of a hollow cone are dropped on a fixed sheet base material fixed at the same position instead of the moving sheet base material to complete the polymerization. When the water-absorbing composite sheet having the polymer adhered on the fixed sheet substrate was obtained, the weight integrated distribution g (r) [w of the water-absorbing polymer with respect to the horizontal distance r (m) from the center of the distribution of the water-absorbing polymer. / W] is expressed by the following correlation equation (1) with a correlation coefficient of 0.97 or more, and parameters r _av [m] and σ [m] in the equation are expressed by the following equations (2) and (3) The continuous production method of a water-absorbent composite sheet according to any one of claims 1 to 3, wherein:

  The method for continuously producing a water-absorbent composite sheet according to any one of claims 1 to 4, wherein the polymerizable monomer is sprayed in a hollow conical shape from a plurality of spray nozzles. The method for continuously producing a water-absorbent composite sheet according to claim 5, wherein a distance dn [m] between adjacent nozzles satisfies the following relationship.
dn ≧ 0.5 × r _av
(R _av is as defined in claim 4) When the amount of the water-absorbing polymer supported on the manufactured water-absorbent composite sheet is statistically analyzed in the direction perpendicular to the moving direction, the average value A _av and the standard deviation Aσ satisfy the following relationship: The continuous manufacturing method of the water absorptive composite sheet according to any one of claims 1 to 6.
Aσ ≦ 0.5 × A _av The said superposition | polymerization is started by mixing the following 1st liquid and 2nd liquid in a gaseous phase, The continuous manufacturing method of the water absorptive composite sheet in any one of Claims 1-7.
1st liquid: The liquid which consists of a polymerizable monomer solution containing either one of the oxidizing agent and reducing agent which comprise a redox type | system | group initiator.
Second liquid: A liquid comprising a solution containing the other of the oxidizing agent or reducing agent contained in the first liquid, or the other of the oxidizing agent or reducing agent contained in the first liquid and a polymerizable monomer.

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